Recent advances in ironmaking are making hot metal relatively more attractive for use in mini-mills. However for a mini-mill effectively to use such hot metal, in lieu of part or all of the scrap metal heretofore employed, it must decarburize the hot metal. Furthermore such decarburization must be rapidly carried out. This is particularly the case where sequence casting is carried out. A major process step in steel refining is decarburization, hence the need for rapid decarburization.
However, rapid decarburization, as practised in a basic oxygen furnace, for example, has been associated with a number of disadvantages. One such disadvantage is the increased risk of slopping caused by the increased vigor of the decarburization reaction. Another disadvantage is a loss of carbon end point accuracy. A third disadvantage is inefficiency caused by localized imbalances of oxygen to carbon causing some oxygen to react with iron and thus reducing yield.
Furthermore, the recent advances in ironmaking tend to produce high-sulfur hot metal. Consequently, the material must be desulfurized as well as decarburized. Moreover, even in a conventional integrated steel mill, there is increased pressure to produce low-sulfur steel. It is desirable to provide a process which can rapidly decarburize a steel melt and also desulfurize the steel melt.
Still further, it is desirable to carry out, in addition to decarburization and desulfurization, other refining steps such as deoxidation and degassing, in an efficient manner compatible with rapid decarburization.
One well known steelmaking process which can achieve high quality in these other steps is the argon-oxygen decarburization (AOD) process. Thus it is desirable to provide a rapid decarburization process which can be used in conjunction with the AOD process.
It is therefore an object of this invention to provide a process for the rapid decarburization of a steel melt.
It is another object of this invention to provide a process for the rapid decarburization of a steel melt while avoiding to a large extent an increased risk of slopping.
It is still another object of this invention to provide a process for the rapid decarburization of a steel melt with excellent carbon end point accuracy.
It is a further object of this invention to provide a process for the rapid decarburization of a steel melt wherein sufficient heat is generated to enable melting of scrap and minimization of fuel element consumption.
It is a still further object of this invention to provide a process for the rapid decarburization of a steel melt while additionally attaining good desulfurization of the steel melt.
It is yet another object of this invention to provide a process for the rapid decarburization of a steel melt while additionally attaining good deoxidation and degassing of the steel melt.
It is still a further object of this invention to provide a process for the rapid decarburization of a steel melt which is compatible with the AOD process.